Sound loop breaks without user input

[dmrib]

During development I realized that sometimes Chrome would not play the audio correctly, giving the following error on console:

The AudioContext was not allowed to start. It must be resumed (or created) after a user gesture on the page.

This happens because we are currently playing the audio without a effective way of giving the option to our users of knowing that a track will be played on that website.

https://github.com/processing/p5.js-website/issues/396
https://developers.google.com/web/updates/2017/09/autoplay-policy-changes#webaudio

We must change the behavior of the sketch to only play audio after some kind of user input.

[dmrib]

I just had a good idea to solve this:

What if instead of starting the terrain scene at the sketch execution, we create a Start button on a kind of welcome screen that would handle this event?

This will also be probably useful to make us able to collect the webcam stream from the user.

[anothergoldenmonkey]

Seems like a valid solution. 👍